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Q1. Pollen grains of rice and wheat remain viable for

• 1) 0.5 hours
• 2) 1 hour
• 3) 24 hours
• 4) 240 hours

Solution

In case of rice and wheat, the pollen grains remain viable for a very less time, about 30 minutes.

Q2. “Incompatibility is a natural barrier in the fusion of gametes”. Justify the statement. 

Solution

1. Nature has developed both structural as well as chemical barriers which restrict fertilisation in organisms. 2. Chemical incompatibility of pollen prevents fertilisation between unrelated plant species. 3. Structural barriers like placement of anthers and stigma at different positions prevent self pollination and promote cross pollination.

Q3. Starting from the innermost part, the correct sequence of parts in an ovule are

• 1) Egg, integument, embryo sac and nucellus.
• 2) Egg, embryo sac, nucellus and integument.
• 3) Egg, nucellus, embryo sac and integument.
• 4) Embryo sac, nucellus, integument and egg.

Solution

The structure of an ovule shows that eggs are the innermost part of the ovule followed by the embryo sac, which contains the egg apparatus, followed by the nucellus, which is surrounded by integuments.

Q4. The nucleus in some seeds found on the outer side of the endosperm is known as

• 1) Perisperm
• 2) Hypocotyl
• 3) Tegmen
• 4) Testa

Solution

Generally in seeds, the nucleus is used up. However, in certain cases where it is not used up, it forms a thin layer on the outside of the endosperm and is known as the perisperm.

Q5. Yucca is pollinated by

• 1) Wind
• 2) Tageticula
• 3) Blastophaga
• 4) Colpa aurea

Solution

Yucca has a close obligatory symbiotic relation with its insect pollinator Tageticula (a moth).

Q6. Fusion of a male gamete with an egg in the embryo sac is called

• 1) Syngamy
• 2) Double fertilisation
• 3) Autogamy
• 4) Triple fusion

Solution

One of the male gametes moves towards the egg cell and fuses with its nucleus thus completing syngamy.

Q7. Double fertilisation involves

• 1) None of the above
• 2) Development of antipodal cells
• 3) Double Fertilisation
• 4) Syngamy + triple fusion

Solution

One of the male gametes moves towards the egg cell and fuses with its nucleus thus completing syngamy. This results in the formation of a diploid cell, the zygote. The other male gamete moves towards the two polar nuclei located in the central cell and fuses with them to produce a triploid primary endosperm nucleus. This is called triple fusion. This completes the process of double fertilisation.

Q8. When pollen is transferred from anther of a flower to stigma of another flower of the same plant, pollination is referred to

• 1) Allogamy
• 2) Geitonogamy
• 3) Xenogamy
• 4) Siphonogamy

Solution

Allogamy is a type of sexual reproduction in plants in which pollen is transferred from one flower to the stigma of another. Xenogamy is the transfer of pollen grains from the anther to the stigma of a different plant. Siphonogamy is a condition in plants in which the pollen tubes are developed for the transfer of male cells to the egg.

Q9. Which of the following plants does not show self-pollination?

• 1) Rye
• 2) Rice
• 3) Jute
• 4) Brinjal

Solution

Rye shows cross-pollination, while the rest show self-pollination.

Q10. Explain the process of artificial hybridisation to get improved crop variety in: (i) plants bearing bisexual flowers (ii) female parent producing unisexual flowers. 

Solution

If a plant breeder desires to cross a particular plant with desired pollen grains, a bisexual flower is artificially transformed into a female flower by removing its stamens in bud condition without affecting the female reproductive organs. This process is called emasculation. The emasculated flower is immediately enclosed in a bag to prevent pollination by unwanted pollen. This process is called bagging. Then, mature and viable pollen grains are collected from the male parent, the bag is opened and the pollen grains are dusted on the stigma. The bag is replaced immediately. The technique of emasculation is applied only when artificial pollination is carried out in a bisexual flower. If the female parent produces unisexual flowers, emasculation is not needed. The unisexual flower is bagged before the flowers open.

Q11. Even though each pollen grain has two male gametes, why are at least 10 pollen grains and not 5 pollen grains required to fertilise 10 ovules present in a particular carpel?

Solution

Even though each pollen grain has two male gametes, atleast 10 pollen grains required to fertilise 10 ovules present in a particular carpel instead of 5 pollen grains because only one male gamete is involved in syngamy or the fusion of male gamete with the egg cell.

Q12. The phenomenon wherein, the ovary develops into a fruit without fertilisation is called

• 1) Parthenocarpy
• 2) Asexual reproduction
• 3) Sexual reproduction
• 4) Apomixis

Solution

Some plants are able to produce fruits without fertilisation. This phenomenon is called parthenocarpy.

Q13. Chiropterophily means

• 1) Pollination by snails
• 2) Pollination by bats
• 3) Pollination by insects
• 4) Pollination by wind

Solution

Pollination by insects is called entomophily. Pollination by wind is called anemophily. Pollination by snails is called malacophily.

Q14. The type of pollination that brings genetically different types of pollen grains to the stigma of a plant is

• 1) Xenogamy
• 2) Chasmogamy
• 3) Geitonogamy
• 4) Autogamy

Solution

Geitonogamy is a kind of pollination in which pollen from the anther of a flower is transferred to the stigma of another flower borne on the same plant. Chasmogamous flower opens at maturity, exposing stamens and style to allow fertilisation. Autogamy is a kind of pollination in which pollen from the anther of a flower is transferred to the stigma of the same flower.

Q15. The ovule found in Opuntia is of which type?

• 1) Circinotropous ovule
• 2) Campylotropous ovule
• 3) Amphitropous ovule
• 4) Orthotropous ovule

Solution

The circinotropous ovule is straight with the micropyle facing upwards. The funicle is elongated and appears coiled shape and completely encircles the ovule. In the beginning, the ovule is orthotropous, but it becomes circinotropous as it develops. This type of ovule is seen in Opuntia flowers.

Q16. Parthenocarpic fruits are developed by the application of

• 1) Cytokinins and gibberellins
• 2) Auxins and gibberellins
• 3) Auxins and cytokinins
• 4) Cytokinins and abscisic acid

Solution

In horticultural techniques, parthenocarpic fruits are artificially developed by the application of low concentration of auxins and gibberellins.

Q17. In Meiosis-I, the cells always divide along which plane?

• 1) Transverse
• 2) Random
• 3) Lateral
• 4) Longitudinal

Solution

In Meiosis-I, the cells always divide along the transverse plane.

Q18. Funnel-shaped corolla is an adaptation of which type of flowers?

• 1) Anemophilous flowers
• 2) Entomophilous flowers
• 3) Hydrophilous flowers
• 4) Ornithophilous flowers

Solution

Ornithophilous flowers or flowers pollinated by birds have a funnel-shaped corolla to allow access to the bird’s beak or tongue to reach to the nectarines.

Q19. The flowers of brinjal are referred to as chasmogamous while that of beans are cleistogamous. How are they different from each other?  

Solution

Flowers of brinjal are similar to flowers of other species where anthers and stigma are exposed. Such flowers are called chasmogamous flowers. On the other hand, the flowers of beans remain closed to ensure self-pollination. Such flowers which remain closed so that cross-pollination does not occur are called cleistogamous flowers.

Q20. Self-sterility implies

• 1) Inability to mate with members of the same species
• 2) Reproduction via vegetative means
• 3) Inability to mate
• 4) Inability to fertilise itself

Solution

Self-sterility or self-incompatibility to mate with members of the same species is known as self-sterility.

Q21. The inner layer of the exine is

• 1) Nexine
• 2) Sexine
• 3) Tectum
• 4) Endosexine

Solution

The exine is made of two major layers—the outer sexine and the inner nexine. The sexine is further divided into the outer tectum and the inner endosexine. The nexine is made of the inner endexine and the outer foot layer.

Q22. (a) Mention any four strategies adopted by flowering plants to prevent self-pollination. (b) Why is geitonogamy also referred to as genetical autogamy?   

Solution

(a) Strategies adopted by flowering plants to prevent self-pollination: 1. Herkogamy: Flowers possess some mechanical barrier on their stigmatic surface to avoid self-pollination. 2. Dichogamy: Pollen and stigma of the flower mature at different times to avoid self-pollination. 3. Self-incompatibility: In same plants, the mature pollen fall on the receptive stigma of the same flower but fail to bring about self-pollination. 4. Male sterility: The pollen grains of some plants are not functional. Such plants set seeds only after cross-pollination. 5. Dioecism: Cross-pollination always occurs when the plants are unisexual and dioecious. 6. Heterostyly: The flowers of some plants have different lengths of stamens and styles so that self-pollination is not possible. (b) Geitonogamy is also referred to as genetical autogamy because it refers to the fusion of male and female gamete from genetically similar plant.

Q23. One flower of Cannabis produces how many pollen grains?

• 1) 5000
• 2) 500000
• 3) 50
• 4) 5

Solution

A single flower of Cannabis produces about 500000 pollen grains.

Q24. In the sixteen-cell stage of the embryo in dicots, the eight protodermal cells show which kind of division? 

• 1) Periclinal division
• 2) Lateral division
• 3) Transverse division
• 4) Anticlinal division

Solution

In the sixteen-cell stage of the embryo in dicots, the eight protodermal cells divide further by anticlinal division to form the embryonic surface layer, while the inner eight cells divide in different planes to form the ground meristem and procambium.

Q25. Flowers of Aristolochia smell of

• 1) Rotten meat
• 2) Decaying tobacco
• 3) Human dung
• 4) Honey

Solution

Aristolochia is an entomophilous flower and smells like decaying tobacco.

Q26. Draw a vertical section of a maize grain and label (i) pericarp (ii) scutellum (iii) coleoptiIe and (iv) radicle.

Solution

Vertical section of maize grain      

Q27. Wind pollination is common in

• 1) Lilies
• 2) Orchids
• 3) Legumes
• 4) Grasses

Solution

Wind pollination describes the process of the transfer of pollen from one individual plant to another, whereby the pollen is carried by air currents. This occurs mostly in grasses and gymnosperms.

Q28. Banana is a parthenocarpic fruit whereas oranges show polyembryony. How are they different from each other with respect to seeds? 

Solution

Banana fruits are seedless. Such fruits are called parthenocarpic, i.e., they produce embryo without fertilisation. The seeds of oranges have many embryos of different sizes and shapes. The orange seeds develop many embryos due to polyembryony.

Q29. The outermost layer of maize endosperm is known as

• 1) Tapetum
• 2) Aleurone
• 3) Perisperm
• 4) Endothecium

Solution

The aleurone layer is the outermost layer of the endosperm. Perisperm, tapetum and endothecium form the inner layers of the maize grain.

Q30. The endosperm cells in angiosperms are

• 1) Haploid
• 2) Tetraploid
• 3) Triploid
• 4) Diploid

Solution

The primary endosperm nucleus divides and after many divisions fills the seed around the embryo with a triploid tissue called the endosperm.

Q31. Among the animals, insects particularly bees are the dominant pollinating agents. List any four characteristic features of insect-pollinated flowers.

Solution

Characteristic features of insect-pollinated flowers: 1. Flowers are large. 2. Colourful petals of flower. 3. Presence of fragrance. 4. Rich in nectar.

Q32. (a) Draw a labelled longitudinal view of an albuminous seed. (b) How are seeds advantageous to flowering plants?

Solution

(a) Longitudinal view of an albuminous seed       (b) Seeds contain food to nourish the embryo during germination and possess better adaptive strategies for dispersal to new habitats. These are formed by sexual reproduction with new variations and better genetic combinations. So, the seeds advantageous to flowering plants.

Q33. In the given figure of a dicot embryo, label the parts (A) and (B) and give their functions.      

Solution

A: Plumule Function: To form the shoot system B: Cotyledons Function: Storage of food 

Q34. Chalazogamy can be observed in

• 1) Casuarina
• 2) Lily
• 3) Populus
• 4) Cucurbita

Solution

When the pollen tube enters the ovule through the chalazal end, it is known as chalazogamy. It is observed in Casuarina.

Q35. If the diploid number of chromosomes in an angiospermic plant is 16, mention the number of chromosomes in the endosperm and antipodal cell.

Solution

The diploid (2n) number of chromosomes in an angiospermic plant is 16. So, the number of chromosomes in endosperm (3n) is 24 and that in antipodal cells (2n) is 16. 

Q36. Name the type of flower which favours cross-pollination.

Solution

The flowers which favour cross-pollination are chasmogamous flowers. They develop exposed anthers and stigma.

Q37. Why is the process of fertilisation in a flowering plant referred to as double fertilisation? Explain.

Solution

Fertilisation in flowering plants is referred to as double fertilisation because both the male gametes of the same microspore take part in fusion. One fuses with the egg to form the diploid zygote, and the other fuses with the two polar nuclei (or secondary nuclei) to form the triploid primary endosperm nucleus.

Q38. Differentiate between geitonogamy and xenogamy.

Solution

Difference between geitonogamy and xenogamy   Geitonogamy  Xenogamy  Transfer of pollen grains from the anther to the stigma of another flower of the same plant.  Transfer of pollen grains from the anther to the stigma of the different plant. Does not provide an opportunity for gametic recombination.  Provides an opportunity for gametic recombination.  

Q39. Indicate the stages where meiosis and mitosis occur (1, 2 or 3) in the flowchart.        

Solution

1. Meiosis 2. Mitosis 3. Mitosis

Q40. Mention two strategies evolved to prevent self-pollination in flowers.

Solution

Cross-pollinating flowers develop the following strategies to prevent self-pollination : 1. Protogyny (when gynoecium matures earlier than androecium) or Protandry (when androecium matures and sheds pollen before maturation of gynoecium) 2. Self incompatibility

Q41. Trace the development of microsporocyte in the anther to a mature pollen grain.

Solution

As the anther develops, the cells of the sporogenous tissue undergo meiotic divisions to form microspore tetrads. As each cell of the sporogenous tissue is capable of giving rise to a microspore tetrad, each one is a potential pollen or microspore mother cell. The process of formation of microspores from a pollen mother cell (PMC) through meiosis is called microsporogenesis. As the anthers mature and dehydrate, the microspores dissociate from each other and develop into pollen grains. Inside each microsporangium, several thousands of microspores or pollen grains are formed that are released with the dehiscence of the anther.

Q42. a) Cleistogamous flowers are strictly self pollinating”. Explain. b) What is the disadvantage of this phenomenon?

Solution

a) Cleistogamous flowers do not open at all and therefore, fertilisation is always between the gametes of the same flower. b) Continued self pollination results in inbreeding depression.

Q43. In double fertilisation

• 1) One male gamete fuses with the antipodal, while the other fuses with the diploid nucleus
• 2) Two male gametes fuse with two eggs
• 3) One male gamete fuses with the egg, while the other fuses with the antipodal
• 4) One male gamete fuses with the egg and the other fuses with the secondary nucleus

Solution

One of the male gametes moves towards the egg cell and fuses with its nucleus thus completing syngamy. This results in the formation of a diploid cell, which is the zygote. The other male gamete moves towards the two polar nuclei located in the central cell and fuses with them to produce a triploid primary endosperm nucleus. This completes the process of double fertilisation.

Q44. In the embryo sac, how many nuclei differentiate to form the antipodal cells?

• 1) 4
• 2) 1
• 3) 3
• 4) 2

Solution

During embryo sac development, four nuclei are found at the chalazal and micropylar ends. Of the four nuclei at the chalazal end, three nuclei differentiate to form the antipodal cells.

Q45. Give reasons why (i) Most zygotes in angiosperms divide only after certain amount of endosperm is formed. (ii) Groundnut seeds are exalbuminous and castor seeds are albuminous. (iii) Micropyle remains as a small pore in the seed coat of a seed. (iv) Integuments of an ovule harden and the water content is highly reduced as the seed matures. (v) Apple and cashew are not called true fruits.

Solution

(i) Endosperm is the food laden tissue formed during the development of angiospermous seed which provides essential nutrients to the growing embryo and also the young seedling at the time of seed germination. So, most zygotes in angiosperms divide only after certain amount of endosperm is formed. (ii) The seeds in which the endosperm is used up are called exalbuminous seeds. In groundnut, the endosperm is used and the reserve food material is stored in cotyledons. So, groundnut seeds are exalbuminous. The seeds having ample amount of endosperm tissue are called albuminous seeds. Castor seeds have persistent endosperm. So, castor seeds are albuminous.   (iii) Double fertilisation in angiosperms brings about some changes in the ovule during the development of seed. The micropyle remains in the form of a fine pore on the surface of seed to allow the entry of water during seed germination.   (iv) Integuments of an ovule harden and the water content is highly reduced as the seed matures to ensure the survival of seeds.   (v) The fruit derived from the ovary of a flower not associated with any non-carpellary part is called a true fruit. In apple and cashew, the main edible part of the fruit is the fleshy receptacle. So, they are not true fruits. Such fruits derived from the ovary along with other accessory floral parts are called false fruits.

Q46. Give the scientific name of a plant which came to India as a contaminant with imported wheat and caused pollen allergy.

Solution

Parthenium, which is a noxious weed, came to India as a contaminant with imported wheat and caused pollen allergy. 

Q47. Why are pollen grains produced in enormous quantity in maize?

Solution

Pollen grains are produced in enormous quantity in maize to ensure pollination as maize is pollinated by wind. 

Q48. (a) Draw a schematic labelled diagram of a fertilised embryo sac of an angiosperm.

Solution

(a) Fertilised embryo sac of an angiosperm        

Q49. Mention the reasons for the difference in ploidy of zygote and primary endosperm nucleus in an angiosperm.

Solution

Zygote is formed by syngamy, so it is diploid in nature, and primary endosperm nucleus is formed by the fusion of secondary diploid nucleus with one of the male gamete, so it is triploid in nature.

Q50. Continued self pollination leads to inbreeding depression. List three devices which flowering plants have developed to discourage self pollination?

Solution

Devices developed by flowering plants to discourage self pollination are: (a) Release of pollen and stigma receptivity is not synchronised in some species (b) Anther and stigma are at different position/heights in some plants (c) Self-incompatibility-a genetic mechanism

Q51. What will be the fate of the following structures in an angiospermic plant? Ovary wall, ovule, zygote, outer integument, inner integument and primary endosperm nucleus.

Solution

Ovary wall: Pericarp Ovule: Seed Zygote: Embryo Outer integument: Testa Inner integument: Tegmen Primary endosperm nucleus: Endosperm

Q52. Some plants have a mechanism of shedding of pollen before the maturation of stigma. Why? 

Solution

Some plants have a mechanism of shedding of pollen before the maturation of stigma to prevent self-pollination.

Q53. Differentiate between microsporogenesis and megasporogenesis. What type of cell division occurs during these events? Name the structures formed at the end of these two events.

Solution

Microsporogenesis: Process of formation of microspore from the pollen mother cell. Megasporogenesis: Process of formation of megaspore from megaspore mother cell. Meiotic division occurs in both the events. Microsporogenesis results in the formation of pollen grains, while megasporogenesis results in the formation of megaspores.

Q54. In a young anther, a group of compactly arranged homogenous cells were observed in the centre of each microsporangium. What is the name given to these cells?

Solution

Sporogenous tissue comprises of compactly arranged homogenous cells observed in the centre of each microsporangium. 

Q55. A bilobed and dithecous anther has 100 microspore mother cells per microsporangium. How many male gametophytes can it produce?

Solution

Each microsporangium has 100 microspore mother cells which form 400 microspores by meiosis (100 × 4). In an anther, there are four microsporangia. So, the total number of microspores will be 4 × 400 = 1600. As each microspore forms one male gametophyte, 1600 male gametophytes can be produced.

Q56. Draw a labelled diagram of the sectional view of a mature pollen grain in angiosperms. Explain the functions of its different parts.

Solution

Structure of mature pollen grains in angiosperms.       Functions of the parts of pollen grain: A mature pollen grain has a two-layered wall—the outer exine and inner intine. The wall encloses a large vegetative cell containing vegetative nucleus and a lenticular generative cell. Their functions are as follows: 1. Exine: The outer thick exine layer is made up of sporopollenin which is resistant to physical and biological decomposition. It provides protection during the hazardous journey of pollen from the anther to stigma. There are one or many germ pores on the pollen surface which are directly or indirectly associated with its germination. 2. Intine: The intine is pecto-cellulosic in nature. It is associated with the formation of the pollen tube. 3. Vegetative cell: The vegetative cell is large and contains abundant food reserve. It has a large vegetative nucleus. The function of the vegetative cell is to provide the medium for the movement of male gametes inside the pollen tube. 4. Generative cell: The generative cell cytoplasm is highly reduced but it contains the usual cell organelles. It divides mitotically to produce two functional male gametes.

Q57. (a) Draw the embryo sac of a flowering plant and label: (i) Central cell. (ii) Chalazal end. (iii) Synergids. (b) Name the cell that develops into an embryo sac and explain how this cell leads to the formation of embryo sac. (c) Mention the role played by the various cells of the embryo sac. (d) Give the role of filiform apparatus.

Solution

(a) Embryo sac of a flowering plant.       (b) Functional megaspore. The nucleus of the functional megaspore divides mitotically to form two nuclei which move to opposite poles and form the 2-nucleate embryo sac. (c) Egg: Fuses with the male gamete to form zygote or the future embryo. Synergid: Absorption of nutrients, attracts and guides the pollen tube. Central cell: After fusion with the second male gamete, it forms the primary endosperm cell which gives rise to the endosperm. (d) The filiform apparatus guides the entry of pollen tube into the embryo sac.